Automatic transmission system

ABSTRACT

An automatic transmission system having a speed changing unit including a torque converter and speed-changing gear means, actuators for varying the meshing engagement of the gears, a hydraulic circuit for controlling the actuators, and an electronic circuit. In the apparatus, the electronic circuit computes the ratio between the rotating speed of the input shaft of the torque converter and the rotating speed of the input or output shaft of the speed-changing gear means to deliver an output signal which is used to actuate a distributing valve in the hydraulic actuating circuit to effect the changing of speed.

United States Patent Wakamatsu et al. 1 Feb. 15, 1972 [54] AUTOMATIC TRANSMISSION SYSTEM [56] References Cited [72] Inventors: Hisato Wakamatsu, Kariya-shi; Takaaki UNITED STATES PATENTS Kato, Toyohashi-shi; Mamoru Kawakubo; 3 354 744 11/1967 K uhnle et al ..74/866 X f bah xanya'sh" 3,448,640 6/l969 Nelson ....74/7s2 x 3,478,851 11/1969 Smyth et al. ..74/866 x [73] Assignee: Nippon Denso Kabushiki Kaisha, Kariyahi Japa Primary ExaminerArthur T. McKeon Attmey -Cushman, Darby & Cushman [22] Frled: Sept. 16, 1969 21 Appl. No.: 858,300 [57] ABSTRACT An automatic transmission system having a speed changing unit including a torque converter and speed-changing gear [30] Forelgn Apphcauon Pnonty Data means, actuators for varying the meshing engagement of the Oct. 28, 1968 Japan ..43/78388 gears, a hydraulic circuit for controlling the actuators, and an electronic circuit. In the apparatus, the electronic circuit com- [52] U.S. Cl ..74/752, 74/866 pu es he ratio between the rotating speed of the input shaft of [51] Intel ....Fl6h 42, F16h 19/00 the torque converter and the rotating speed of the inp or [58] Field of Search ..74/752, 866 output shaft of the p hanging gear means to deliver an output signal which is used to actuate a distributing valve in the hydraulic actuating circuit to effect the changing of speed.

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ATTORNEYS AUTOMATIC TRANSMISSION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a transmission system for automotive vehicles and the like, and more particularly to an automatic transmission system comprising a hydraulic torque converter and a multispeed gear-changing means.

2. Description of the Prior Art In an automatic transmission system employed heretofore in common passenger cars, the speed-changing point is generally determined from a signal representing the vehicle speed (taken from the output shaft of multispeed gear-changing means) and a signal representing the negative pressure (boost pressure) in the air intake pipe of the prime mover or internal combustion engine or a signal representing the amount of depression of the accelerator pedal actuated by the driver. A commonly employed method comprises obtaining these signals in the form of a high and a low hydraulic pressure, determining the speed-changing point on the basis of the interrelation between these two hydraulic pressures, and opening and closing related valves for selectively hydraulically operating an actuator such as a multiple disc clutch and a brake band. Thus, in the conventional automatic transmission system which is wholly controlled by means of hydraulic pressure, the detected signals in the form of hydraulic pressures are subject to errors and therefor are generally inaccurate. This means that the speed-changing point is also frequently subjected to error. Further, the hydraulic actuating circuit is generally complex and it is not an easy matter to impart thereto an improved function over the existing function. For example, when abrupt deceleration is required while the vehicle is going up a slope at a relatively high speed, release of the depression pressure imparted to the accelerator pedal causes gear changing into a position one stage higher before the desired deceleration takes place, and redepression of the accelerator pedal immediately thereafter for the purpose of acceleration causes gear changing into a position one stage lower, thus putting the driver to inconvenience. Moreover, when the vehicle is going down a decline at a relatively high speed, the speed tends to increase in spite of the fact that engine braking is required, and gear changing to the low gear side cannot be automatically effected. In such a case, commonly, the driver must manually shift the gear to a lower gear in order to avoid such inconvenience. Thus, the conventional automatic transmission system involves fundamental defects due to the fact that the speed-changing point is determined solely on the basis of the load on the internal combustion engine and the vehicle speed, and that no consideration is given to factors such as the internal state of the transmission system.

SUMMARY OF THE INVENTION The present invention is featured by the fact that the slip of a torque converter constitutes an important element of a transmission system, and this serves as the main factor for determining the speed changing point. An electronic circuit is introduced for the purpose of determining the speed transition point, so that the electronic circuit delivers speed changing instructions. Which are most suitable for a specific condition of speed variation, thereby to operate suitable actuators through a hydraulic actuating circuit to effect the desired control.

It is a primary object of the present invention to provide an automatic transmission system which possesses an appropriate speed-changing function even when the engine is running with engine brake while going down a slope, needless to say under normal running conditions, which possesses a simplified mechanical structure for the hydraulic system associated with the actuators, which includes improved means for preventing an error in the speed-changing point due to a variation in the hydraulic pressure, and which possesses a more accurate and higher operating function than heretofore.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a speed-changing unit preferably used in an automatic transmission system embodying the present invention.

FIGS. 2, 3, 4 and 5 are diagrammatic views illustrating the operation of a hydraulic actuating circuit when the present invention is adapted to a two-forward-speed automatic transmission system, in which the hydraulic actuating circuit is shown in its N, DL, DH and R positions, respectively.

FIG. 6 is a graph showing one example of the speed-changing region.

FIG. 7 is a block diagram showing the structure of an electronic operation circuit preferably used in the embodiment of the present invention.

FIGS. 8a and 8b are a side elevational view and a front elevational view, respectively, of a revolution detector preferably used in the apparatus.

FIG. 9 is a block diagram showing the structure of a revolution operating circuit in the circuit shown in FIG. 7.

FIG. 10 is a graphic illustration of the operating voltage waveforms in the revolution operating circuit shown in FIG. 9.

FIGS. 11a and 1112 are a block diagram and a circuit diagram, respectively, showing the structure of a slip operating circuit in the circuit shown in FIG. 7.

FIG. 12 is a circuit diagram showing the structure of a revolution-setting operating circuit in the circuit shown in FIG. 7.

FIGS. 13a and 13b are a block diagram and a circuit diagram, respectively, showing the structure of a synchronous timing holding circuit in the circuit shown in FIG. 7.

FIG. 14 is a graphic illustration of the operating voltage waveforms in the synchronous timing holdin'g circuit shown in FIG. 13.

FIGS. 15a and 15b are a block diagram and a circuit diagram, respectively, of a bistable memory circuit in the circuit shown in FIG. 7.

FIG. 16 is a graphic illustration of operating voltage waveforms in the bistable memory circuit shown in FIG. 15.

FIG. 17 is a block diagram illustrating the manner of operation of gear changing from low gear to high gear in the circuit shown in FIG. 7.

FIG. 18 is a block diagram illustrating the manner of operation under the continuous application of a synchronous timing holding signal after the gear changing from low to high gear.

FIG. 19 is a block diagram illustrating the manner of operation under the disappearance of the synchronous timing holding signal after gear changing from low to high gear.

FIG. 20 is a block diagram illustrating the manner of operation when the slip ratio is reduced to a value less than 0.6 in the course of gear changing from high to low gear.

FIG. 21 is a block diagram illustrating the manner of operation under a continuous synchronous timing holding signal after gear changing from high to low gear.

FIG. 22 is a block diagram illustrating the manner of operation under the disappearance of the synchronous timing holding signal after gear changing from high to low gear.

FIG. 23 is a diagrammatic view illustrating the operation of a hydraulic actuating circuit when the present invention is applied to a three-forward-speed automatic transmission system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is the first feature of the present invention that the automatic transmission system is composed essentially of three parts, that is, a speed-changing unit equipped with a hydraulic torque converter, a hydraulic actuating circuit, and an electronic operation circuit and a logic circuit as apparent from an embodiment thereof which will be described in detail hereunder. 

1. An automatic transmission system comprising a speed-changing unit equipped with a torque converter including a torque converter pump operatively connected with an input shaft of said speed-changing unit and a torque converter turbine operatively connected with an input shaft for speed-changing gear means, frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed-changing gear means of said speed-changing unit, a hydraulic actuating circuit including a speed-changing region setting valve and a distributing valve for distributing hydraulic fluid to said frictionally engaging means for controlling said frictionally engaging means, first detecting means for generating an electrical signal which is proportional to the rotating speed of the input shaft of the torque converter, second detecting means for generating an electrical signal which is proportional to the rotating speed of either the input of output shaft of said speed-changing gear means, an operating circuit operative, by receiving the electrical output signals from said first and second detecting means, to make an arithmetic operation of the ratio between the rotating speed of the input shaft of said torque converter and the rotating speed of the input shaft or output shaft of said speed-changing gear means, and means operative, in response to an output signal from said operating circuit, to actuate the distributing valve in said hydraulic actuating circuit, said operating circuit being composed of two potentiometers and a differential amplifying circuit including a differential comparison circuit and an amplifying circuit, operative in such a manner that, when the ratio between the rotating speeds lies in a predetermined range, it generates an output signal for actuating said distributing valve thereby to vary the meshing engagement of the gears in said speed-changing gear means.
 2. An automatic transmission system comprising a speed-changing unit equipped with a torque converter including a torque converter pump operatively connected with an input shaft of said speed-changing unit and a torque converter turbine operatively connected with an input shaft of speed-changing gear means, frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed-changing gear means of said speed-changing unit, a hydraulic actuating circuit including a speed-changing region-setting valve and a distributing valve for distributing hydraulic fluid to said frictionally engaging means for controlling said frictionally engaging means, first detecting means for generating an electrical signal which is propoRtional to the rotating speed of the input shaft of the torque converter, second detecting means for generating an electrical signal which is proportional to the rotating speed of either the input or output shaft of said speed-changing gear means, an operating circuit operative, by receiving the electrical output signals from said first and second detecting means, to make an arithmetic operation of the ratio between the rotating speed of the input shaft of said torque converter and the rotating speed of the input or output shaft of said speed-changing gear means, means operative, in response to an output signal from said operating circuit, to actuate the distributing valve in said hydraulic actuating circuit, and a revolution-setting operating circuit composed of a Schmitt circuit and a phase inversion circuit and acting as two revolution-setting operating circuits which generate an output signal when the rotating speed of the input or output shaft of said speed-changing gear means is greater or smaller than a predetermined value, the output signal from said revolution-setting operating circuit and the output signal from said operating circuit for making an arithmetic operation of the ratio between the rotating speeds being used to actuate said distributing valve thereby to vary the meshing engagement of the gears in said speed-changing gear means.
 3. An automatic transmission system comprising a speed-changing unit equipped with a torque converter including a torque converter pump operatively connected with an input shaft of said speed-changing unit and a torque converter turbine operatively connected with an input shaft of speed-changing gear means, frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed-changing gear means of said speed-changing unit, a hydraulic actuating circuit including a speed-changing region setting valve and a distributing valve for distributing hydraulic fluid to said frictionally engaging means for controlling said frictionally engaging means, first detecting means for generating an electrical signal which is proportional to the rotating speed of the input shaft of the torque converter, second detecting means for generating an electrical signal which is proportional to the rotating speed of either the input or output shaft of said speed-changing gear means, an input shaft revolution setting operating circuit for generating an electrical output signal when the output signal from said first detecting means reaches a predetermined limit, an operating circuit operative, by receiving the electrical output signals from said first and second detecting means, to make an arithmetic operation of the ratio between the rotating speed of the input shaft of said torque converter and the rotating speed of the input or output shaft of said speed-changing gear means, and means for applying the output signals form both said operating circuits through a bistable memory circuit for actuating the distributing valve in said hydraulic actuating circuit, said bistable memory circuit being composed of a bistable multivibrator and an amplifying circuit.
 4. An automatic transmission system comprising a speed-changing unit equipped with a torque converter including a torque converter pump operatively connected with an input shaft of said speed-changing unit and a torque converter turbine operatively connected with an input shaft of speed-changing gear means, frictionally engaging means for accomplishing the selective meshing engagement of gears in the speed-changing gear means of said speed-changing unit, a hydraulic actuating circuit including a manual speed-changing region-setting valve and a distributing valve for distributing hydraulic fluid to said frictionally engaging means for controlling said frictionally engaging means, first detecting means for generating an electrical signal which is proportional to the rotating speed of the input shaft of the torque converter, second detecting means for generating an electrical signAl which is proportional to the rotating speed of either the input or output shaft of said speed-changing gear means, a slip-operating circuit operative, by receiving the electrical output signal from said first detecting means and the electrical output signal from said second detecting means, to make an arithmetic operation of the ratio between the rotating speed of the input shaft of the torque converter and the rotating speed of the input or output shaft of the speed-changing gear means, an output shaft revolution setting operating circuit for generating an electrical output signal when the output signal from said second detecting means reaches a predetermined limit, means operative, in response to the output signals from both said operating circuits to actuate the distributing valve in said hydraulic actuating circuit, and a synchronous timing holding circuit composed of a differentiation circuit including one phase inversion circuit and two systems of differentiating elements, a rectifying circuit having two diodes, and a monostable multivibrator, said synchronous timing holding circuit being operative to prevent the occurrence of any different speed changing signals for some period of time after said means for actuating said distributing valve has been operated. 